Many of the documents quoted in the book are available online, in which case you will find them linked directly from the Notes at the end of the book.
Other books and sources you may find interesting are linked below. If you follow an Amazon link and purchase something, this site gets a bit of revenue which helps support it.
Joseph Smith, Jr. Teachings of the Prophet Joseph Smith. Deseret Book, 1993.
ALBION’S SEED, by David Hackett Fischer.
One Nation Under Gods: A History of the Mormon Church Paperback – July 29, 2003
by Richard Abanes (Author)
The Mormon War: Zion and the Missouri Extermination Order of 1838 Kindle Edition
by Brandon G. Kinney (Author)
The Religious History of America: The Heart of the American Story from Colonial Times to Today Kindle Edition
by Edwin S. Gaustad (Author), Leigh Schmidt (Author)
Angels and Demons: What Do We Really Know about Them? Kindle Edition
by Peter J. Kreeft
There are many books on Jewish mysticism, but good entry guide (despite the name) is:
Kabbalah For Dummies Kindle Edition
by Arthur Kurzweil (Author)